Fast Adversarial Training with Smooth Convergence

Fast adversarial training (FAT) is beneficial for improving the adversarial robustness of neural networks. However, previous FAT work has encountered a significant issue known as catastrophic overfitting when dealing with large perturbation budgets, \ie the adversarial robustness of models declines to near zero during training. To address this, we analyze the training process of prior FAT work and observe that catastrophic overfitting is accompanied by the appearance of loss convergence outliers. Therefore, we argue a moderately smooth loss convergence process will be a stable FAT process that solves catastrophic overfitting. To obtain a smooth loss convergence process, we propose a novel oscillatory constraint (dubbed ConvergeSmooth) to limit the loss difference between adjacent epochs. The convergence stride of ConvergeSmooth is introduced to balance convergence and smoothing. Likewise, we design weight centralization without introducing additional hyperparameters other than the loss balance coefficient. Our proposed methods are attack-agnostic and thus can improve the training stability of various FAT techniques. Extensive experiments on popular datasets show that the proposed methods efficiently avoid catastrophic overfitting and outperform all previous FAT methods. Code is available at \url{https://github.com/FAT-CS/ConvergeSmooth}

Chemical Characteristics-Based Evolution of Groundwater in Tailan River Basin, Xinjiang, China

Groundwater plays an important role in ecological environment protection in arid and semi-arid areas. Therefore, understanding the characteristics of hydrochemical evolution is of great significance for the sustainable use of groundwater in the area of the Tailan River Basin. The Tailan River Basin is located in an arid, ecologically sensitive area in western China. In this study, we collected 42 groups of representative water samples from the Tailan River Basin and analyzed the chemical distribution in the groundwater using mathematical statistics, Piper and Gibbs diagrams, ion ratio analysis, and hydrogeochemical simulation methods. We also discussed the water–rock interactions in the groundwater hydrochemical evolutionary process. The results were as follows: (1) The chemical types of groundwater changed from HCO3·SO4-Ca·Na to SO4·Cl-Na·Ca, Cl·SO4-Na, and Cl-Na, and the total dissolved solids content increased from less than 1 g/L to more than 40 g/L from the gravel plain to the fine soil plain. (2) The Gibbs diagram, the ion ratio analysis, and the saturation index showed that the groundwater chemical characteristics in the study area were mainly controlled by water–rock interactions, as well as evaporation and concentration. Along the runoff of groundwater, halite and gypsum were dissolved. Nevertheless, dolomite and calcite precipitated. The relationship between the chlor-alkali index and [(Na+ + K+)-Cl−] and [(Ca2+ + Mg2+)-(HCO3− + SO42−)] indicated that cation exchange also affects the chemical composition of groundwater in the area. (3) Through reverse hydrogeochemical simulation, the main water–rock effect of the groundwater runoff process revealed by qualitative analysis was quantitatively verified

Estimation of Groundwater Evapotranspiration of Different Dominant Phreatophytes in the Mu Us Sandy Region

Groundwater evapotranspiration (ETG) estimation is an important issue in semiarid areas for groundwater resources management and environmental protection. It is widely estimated by diurnal water table fluctuations. In this study, the ETG at four sites with different plants was estimated using both diurnal water table and soil moisture fluctuations in the northeastern Mu Us sandy region, in order to identify the groundwater utilization strategy by different dominant phreatophytes. Groundwater level was monitored by ventilatory pressure transducers (Solinst LevelVent, Solinst Canada Ltd.; accuracy ±3 mm), while soil moisture was monitored using EM50 loggers (Decagon Devices Inc., Pullman, USA) in K1 and K14 and simulated by Hydrus-1D in other observation wells. A significant spatial variation of ETG was found within a limited area, indicating a poor representativeness of site ETG for regional estimation. The mean values of ETG are 4.01 mm/d, 6.03 mm/d, 8.96 mm/d, and 12.26 mm/d at the Achnatherum splendens site, Carex stenophylla site, Salix psammophila site and Populus alba site, respectively, for the whole growing season. ETG is more sensitive to depth to water table (DWT) in the Carex stenophylla site than in the Achnatherum splendens site for grass-dominated areas and more sensitive to DWT in the Populus alba site than in Salix psammophila site for tree-dominated areas. Groundwater extinction depths are estimated at 4.1 m, 2.4 m, 7.1 m, and 2.9 m in the Achnatherum splendens site, Carex stenophylla site, Salix psammophila site and Populus alba site, respectively

Freeze-thaw damage assessment of engineered cementitious composites using the electrochemical impedance spectroscopy method

The mechanical properties of engineered cementitious composites (ECC) in service in cold regions can be significantly degraded by periodic freezing and thawing. In this work, the damage degree of freeze–thaw of ECC was systematically assessed by using the electrochemical impedance spectroscopy (EIS) technique. In addition, Nuclear Magnetic Resonance (NMR) Relaxometry measurements were also performed to obtain pore structure parameters, and the uniaxial tensile tests were also carried out to analyse the tensile performance after freeze–thaw cycles. From the acquired results, it was demonstrated that the EIS behaviour of ECC varied with the freeze–thaw cycles. The diameter of the Nyquist curve in high-frequency was gradually reduced by increasing the freeze–thaw cycles. Furthermore, the volume resistance of ECC after freeze–thaw gradually decreased with the increase in the number of freeze–thaw cycles. The simplified microstructure and conductive paths were used to describe the freeze–thaw damage mechanism of ECC. An equivalent circuit model of ECC exposed to freeze–thaw cycles was proposed, and the parameters of the equivalent circuit model were thoroughly analysed. The experimental findings clearly indicate that the EIS method is an appropriate technique for evaluating the damage degree of freeze–thaw of ECC

Robust Multi-Agent Coordination via Evolutionary Generation of Auxiliary Adversarial Attackers

Cooperative Multi-agent Reinforcement Learning (CMARL) has shown to be promising for many real-world applications. Previous works mainly focus on improving coordination ability via solving MARL-specific challenges (e.g., non-stationarity, credit assignment, scalability), but ignore the policy perturbation issue when testing in a different environment. This issue hasn't been considered in problem formulation or efficient algorithm design. To address this issue, we firstly model the problem as a Limited Policy Adversary Dec-POMDP (LPA-Dec-POMDP), where some coordinators from a team might accidentally and unpredictably encounter a limited number of malicious action attacks, but the regular coordinators still strive for the intended goal. Then, we propose Robust Multi-Agent Coordination via Evolutionary Generation of Auxiliary Adversarial Attackers (ROMANCE), which enables the trained policy to encounter diversified and strong auxiliary adversarial attacks during training, thus achieving high robustness under various policy perturbations. Concretely, to avoid the ego-system overfitting to a specific attacker, we maintain a set of attackers, which is optimized to guarantee the attackers high attacking quality and behavior diversity. The goal of quality is to minimize the ego-system coordination effect, and a novel diversity regularizer based on sparse action is applied to diversify the behaviors among attackers. The ego-system is then paired with a population of attackers selected from the maintained attacker set, and alternately trained against the constantly evolving attackers. Extensive experiments on multiple scenarios from SMAC indicate our ROMANCE provides comparable or better robustness and generalization ability than other baselines

The Hydrological Impact of Extreme Weather-Induced Forest Disturbances in a Tropical Experimental Watershed in South China

Tropical forests are frequently disturbed by extreme weather events including tropical cyclones and cold waves, which can not only yield direct impact on hydrological processes but also produce indirect effect on hydrology by disturbing growth and structures of tropical forests. However, the hydrological response to extreme weather-induced forest disturbances especially in tropical forested watersheds has been less evaluated. In this study, a tropical experimental watershed in Hainan Province, China, was selected to investigate the hydrological responses to extreme weather-induced forest disturbances by use of a single watershed approach and the paired-year approach. Key results are: (1) extreme weather-induced forest disturbances (e.g., typhoon and cold wave) generally had a positive effect on streamflow in the study watershed, while climate variability either yielded a negative effect or a positive effect in different periods; (2) the response of low flows to forest discussion was more pronounced; (3) the relative contribution of forest disturbances to annual streamflow (48.6%) was higher than that of climate variability (43.0%) from 1995 to 2005. Given the increasing extreme weather with climate change and their possible catastrophic effects on tropical forests and hydrology in recent decades, these findings are essential for future adaptive water resources and forest management in the tropical forested watersheds.Arts and Sciences, Irving K. Barber School of (Okanagan)Non UBCEarth, Environmental and Geographic Sciences, Department of (Okanagan)ReviewedFacult

Aqp5 Is a New Transcriptional Target of Dot1a and a Regulator of Aqp2

<div><p><em>Dot1l</em> encodes histone H3 K79 methyltransferase Dot1a. Mice with <em>Dot1l</em> deficiency in renal Aqp2-expressing cells (<em>Dot1l^AC</em>) develop polyuria by unknown mechanisms. Here, we report that Aqp5 links <em>Dot1l</em> deletion to polyuria through Aqp2. cDNA array analysis revealed and real-time RT-qPCR validated <em>Aqp5</em> as the most upregulated gene in <em>Dot1l^AC</em> vs. control mice. Aqp5 protein is barely detectable in controls, but robustly expressed in the <em>Dot1l^AC</em> kidneys, where it colocalizes with Aqp2. The upregulation of Aqp5 is coupled with reduced association of Dot1a and H3 dimethyl K79 with specific subregions in Aqp5 5′ flanking region in <em>Dot1l^AC</em> vs. control mice. In vitro studies in IMCD3, MLE-15 and 293Tcells using multiple approaches including real-time RT-qPCR, luciferase reporter assay, cell surface biotinylation assay, colocalization, and co-immunoprecipitation uncovered that Dot1a represses Aqp5. Human AQP5 interacts with AQP2 and impairs its cell surface localization. The AQP5/AQP2 complex partially resides in the ER/Golgi. Consistently, AQP5 is expressed in none of 15 normal controls, but in all of 17 kidney biopsies from patients with diabetic nephropathy. In the patients with diabetic nephropathy, AQP5 colocalizes with AQP2 in the perinuclear region and AQP5 expression is associated with impaired cellular H3 dimethyl K79. Taken together, these data for the first time identify Aqp5 as a Dot1a potential transcriptional target, and an Aqp2 binding partner and regulator, and suggest that the upregulated Aqp5 may contribute to polyuria, possibly by impairing Aqp2 membrane localization, in <em>Dot1l^AC</em> mice and in patients with diabetic nephropathy.</p> </div

Aqp5 is significantly upregulated and coexpressed with Aqp2 in the kidney of <i>Dot1l^AC</i> mice on the normal Na⁺ pellet diet.

<p>(<b>A</b>) Real-time RT-qPCR for expression of Aqp5 in kidney of mice fed the normal Na⁺ pellet diet, with β-actin as internal control. n = 6 mice/group. <i>+/+AC</i>: <i>Dot1l^+/+Aqp2:Cre</i> (<b>B</b>) As in <b>A</b>, agarose gel analysis of the final RT-qPCR products of Aqp5 and β-actin. (<b>C</b>) Sequencing of a regular RT-PCR product from a <i>Dot1l^f/f</i> mouse kidney. A part of the tracing file showing Aqp5 sequence encoding aa 47–55 (GenBank#: EDL04123.1) is given. (<b>D</b>) Representative IF images showing Aqp5 (green) expression in Aqp2⁺ (red) cells in mice as indicated. OM and IM: outer and inner medulla. *: An IC without Aqp5 expression, possibly due to lack of Aqp2Cre-mediated <i>Dot1l</i> ablation. Arrow: PC with strong Aqp2 and weak Aqp5, highlighting the lack of cross reactivity of the two antibodies. Aqp5⁺Aqp2⁻ cells are most likely the intercalated cells derived from the Aqp2-expressing progenitor cells or mature PC <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0053342#pone.0053342-Wu2" target="_blank">[30]</a>. Arrowhead: Colocalization of Aqp5 with Aqp2, which is amplified in the inserts. Scale bar: 50 µM. For more images with lower magnification, see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0053342#pone.0053342.s003" target="_blank">Figure S3</a>.</p